! ---------------------------------------------------------------------------- !
! Daemons.h by Andrew Plotkin and Roger Firth (roger@firthworks.com,
! to whom all problems should be notified).
!
! 2.0 Oct 2001
! Converted to Inform 6 and Glulx by Roger Firth.
!
! 1.0 Oct 1995
! Original version for Inform 5.5 by Andrew Plotkin.
!
! This file is in the public domain.
! ---------------------------------------------------------------------------- !
! Installation: add the lines:
!
! Replace StartDaemon;
! Replace StartTimer;
!
! before your Include "Parser" line. Also, add the line:
!
! Include "daemons";
!
! near the end of your game AFTER you've defined an object which uses a
! "daemon_priority" property.
!
! ---------------------------------------------------------------------------- !
!
! This is a package which you can include to make the daemons and timers of
! the Inform libraries behave predictably. They will execute in the order
! defined by the optional "daemon_priority" property of each object in the
! daemon/timer list. Higher priorities go first; if priorities are equal,
! they execute in the order in which they were started up. The default
! daemon_priority is zero, but you can assign any numerical value to the
! property, including negative ones.
!
! There are a few restrictions:
!
! - daemon_priority must be a simple variable containing a number; it cannot
! be an embedded routine which returns a number.
! - you should assign a new value to a daemon_priority property only while
! the object's daemon/timer is *not* running. This means that if an object
! has both a daemon and a timer, they must run at the same priority.
! - it is illegal to call StartDaemon() or StartTimer() from inside a
! daemon or timer routine. It *is* legal to call StopDaemon() or
! StopTimer() at any time.
!
! A bonus utility routine IsDaemonActive(obj) returns 1 if obj currently has
! an active daemon, 2 for an active timer, 3 for both, 0 for neither.
!
! Here is an example daemon:
!
! Object myDaemon
! with daemon_priority 1000,
! daemon [;
! ...
! ];
!
! ---------------------------------------------------------------------------- !
#ifndef WORD_HIGHBIT; ! Is already defined in Glulx compiler.
Constant WORD_HIGHBIT $8000; ! Topmost bit in Z-machine word, used by
#endif; ! the Library to flag daemons in the_timers.
! GetPriority() is a utility routine which masks out the daemon-or-timer flag
! and fetches the value of the daemon_priority property.
!
[ GetPriority obj;
obj = obj & ~WORD_HIGHBIT;
if (obj provides daemon_priority) return obj.daemon_priority;
return 0;
];
! StartDaemonOrTimer() is a utility routine which inserts the given object
! in the_timers list, at the position defined by its daemon_priority. That is,
! the object is inserted after all objects with a greater-or-equal priority,
! and before all objects with a lesser priority.
!
[ StartDaemonOrTimer obj
i j;
! If obj already in the list, do nothing
for (i=0 : ii == obj) rfalse;
! Compress the list, removing empty slots
for (i=0,j=0 : ii) {
if (i > j) {
the_timers-->j = the_timers-->i;
the_timers-->i = 0;
}
j++;
}
! Check for capacity to run another daemon/timer
active_timers = j;
if (active_timers == MAX_TIMERS) { RunTimeError(4); rfalse; }
! Find the first slot at a lower priority
for (i=0 : ii) < GetPriority(obj)) break;
! Shift upwards that slot and those above it
for ( : j>i : j--) the_timers-->j = the_timers-->(j-1);
! Insert the new object
the_timers-->i = obj;
return ++active_timers;
];
! Replacement for the standard Library version of StartDaemon().
!
[ StartDaemon obj;
StartDaemonOrTimer(obj+WORD_HIGHBIT);
];
! Replacement for the standard Library version of StartTimer().
!
[ StartTimer obj timer;
if (obj.&time_left == 0) { RunTimeError(5, obj); return; }
if (StartDaemonOrTimer(obj)) obj.time_left = timer;
];
! ---------------------------------------------------------------------------- !
System_file;
! IsDaemonActive() tests whether an object's daemon and/or timer is
! currently scheduled to run.
!
[ IsDaemonActive obj
i j;
for (i=0,j=0 : ii == obj) j = 2;
else if (the_timers-->i == obj + WORD_HIGHBIT) j++;
}
return j;
];
! ---------------------------------------------------------------------------- !